Electrodeposition of copper



Patented May 31, 1949 P UNITED STATES PATE T. org es 2,471,918 p ELECTRODEPOSITION OF COPPER Karl S. Willson and David Ellis,*Cleveland,'

Ohio, assignors to The HarshawChemical chm.- pany, Cleveland, Ohio, a corporation of Ohio N Drawing. Application December 12, 1946, Serial No. 715,626

3 Claims. 1

This invention relates to electrodeposition of copper and more particularly to improved processes and solutions for electrodeposition of bright copper.

We have now discovered that by the inclusion in the copper cyanide plating solution of a suitable quantity of an organic compound of the formula.

which is suitably soluble in the solution and stable therein and wherein R represents a radical of.

the class consisting of alkyl and aryl radicals containing not more than six carbon atoms, we are able to produce an electrodeposit of small grain size and having substantial lustre. That is, when such a deposit is made, it can be built up to substantial thickness, three ten thousandths of an inch and more, and still exhibit greatly improved lustre as compared with the usual cyanide copper bath. Agitation of the solution results in improvement in lustre and makes possible the use of much higher current density, e. g. increase from ASF to 60 ASF. Interruption of the current at intervals, e. g. 1 minute on, 10 seconds olf, reversal of the current every few seconds or use of alternating current superimposed on the direct current, all tend to produce improved lustre ,and more uniform deposits.

Examples of compounds which have the requisite solubility and stability are:

2-acetyl thiophene, H);S OOMe 2-benzoylthiophene,( HMS COPh The compound to be suitable should have adequate solubility in the copper cyanide bath to make possible the maintenance in solution of a sufficient quantity of the addition agent to achieve the desired result. The brightening effect or grain size reduction can be achieved in greater or lesser degree with very small amounts of the indicated addition agents. In general the concentration of addition agent should not be less than 0.10 gram per liter and when maximum brightness has been achieved, it is not profitable to increase the concentration further. In general 2.5 grams per liter may be taken as a sufiicient concentration. Any of the compounds mentioned having a solubility in the copper cyanide solution of at least 0.10 gram per liter may be expected to achieve.

2 the benefits of the invention in substantial degree at a concentration of 0.10 gram per liter and they may be used in quantity up to 3.75 grams per liter.

An aqueous alkaline plating bath may be employed containing 4 to 20 ounces of CuCN per gallon (30 to 150 grams per liter) and the requisite amount [of NaCN. The preferred pI-I range is 9.5 to 11.5 but good results may be had from 8.5 to 12.5. Free cyanide content may be from 0 to 11.5 grams per liter or more. In general, increase of free cyanide is desirable with increasing CuCN content. The temperature is preferably maintained between F. and 150 F. although good results can be had between 120 F. and 160 F.

Current is passed through the above indicated solutions from a copper anode to a cathode at a cathode current density of from a very low value up to 60 amperes per square foot.

Preferred solutions and plating conditions would be, for example:

Example I CuCN 120 grams per liter Free cyanide 3.75 grams per liter 2-acetyl thiophene 3.75 grams per liter Water Remainder pI-I 10.5 Temp F. Current density 40 ASE.

Example II CuCN 120 grams per liter Free CN 4.5 grams per liter 2-benzoyl thiophene 3.75 grams per liter Water Remainder pH 10 0 Temp 140 F. Current density 30 ASF.

Having thus described our invention, what we claim is:

1. In a process for electrodepositing bright copper, the step which comprises electrolyzing an aqueous alkaline copper cyanide solution and a minor proportion of a soluble acyl thiophene compound corresponding to the formula where R represents a radical of the class consisting of alkyl and aryl radicals having not more than six carbon atoms, the copper cyanide concentration being from 30 to grams per liter and the concentration of the acyl thiophene coxm pound being from 0.10 to 3.75 grams per liter.

2. In a process for electrodepositing bright copper, the step which comprises electrolyzing an aqueous, alkaline copper cyanide solution and a minor proportion from 0.10 to 3.75 grams per liter of acetyl thiophene.

3. In a, process for electrodepositing bright copper, the step which comprises electrolyzing an aqueous, alkaline copper cyanide solution and a.

minor proportion from 0.10 to 3.75 grams per liter I of benzoyl thiophene.

KARL S. WILLSON. DAVID G. ELLIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,410,844 Signaigo et a1 Nov. 12, 1946 

